This invention relates to plasma thawing systems for thawing frozen bags of plasma or blood, and in particular, to dry plasma thawing systems in which frozen bags of plasma are thawed without direct submersion into a liquid bath.
Storing frozen plasma and then thawing it for transfusions is common practice at health care facilities. Typically, bags of plasma are frozen to preserve the plasma for subsequent use. For this purpose, plasma is usually stored frozen in a sealed prepackaged pouch or bag. Prior to use, the frozen plasma is thawed and heated to a selected temperature.
Before a frozen bag of plasma can be used for a transfusion, the frozen plasma must first be heated to a desired transfusable temperature. To accomplish the thawing of the frozen plasma, a bag of frozen plasma may be placed directly into a liquid bath which is heated to a predetermined temperature to raise the temperature of the plasma. One of the problems with using this type of wet bath to effect plasma thawing is that contamination of the entire bath will occur if a plasma bag inadvertently leaks during the thawing process. Another problem is that contaminants in the bath may be transferred to the bag of plasma. Consequently, as an alternative to thawing the plasma by direct insertion into a wet bath, an overwrap bag can be used to protect the blood product bag and to isolate the bag in case of breakage. The disadvantage of overwrap bags is that they are wet on the outside and handling such bags is inconvenient and creates a breeding ground for bacteria.
A better approach is dry thawing without requiring exposure to water, but ensuring that the temperature of the blood product never exceeds body temperature. Dry thawing with the plasma bag disposed in a vertical orientation has disadvantages because the bath must be drained for loading and refilled for thawing. Horizontal dry thawing overcomes this disadvantage. A dry system of heating the plasma has been utilized in which plasma bags are placed in contact with a bladder filled with heating fluid. The dry system of thawing functions to isolate the plasma bags from the heating fluid while still effecting heat conduction to the bags.
While the use of a dry, or indirect, heating system reduces the possibility that the heating fluid will become contaminated during bag leakage, contamination problems still exist when multiple plasma bags are thawed in an apparatus at the same time. Even in a dry system, if one of the plasma bags leaks, then all of the plasma bags become tainted and must be discarded. Another problem with conventional dry horizontal systems in which one or more plasma bags rest horizontally upon bladders to effect heating is that air pockets or air bubbles have a tendency to form along the top surface of the bladder which is in contact with the bag of plasma. The trapped air pocket acts as an insulator between the heating fluid and the plasma bag thereby decreasing the effectiveness of the thawing apparatus both in terms of time and energy costs. Therefore, it would be advantageous if a dry frozen plasma thawing system was capable of more efficiently thawing more than one plasma bag while preventing contamination from a single bag from causing the whole lot of plasma bags to be discarded.
In accordance with the present invention, a heating apparatus is provided for heating a medical product to a selected temperature. More specifically, the heating apparatus functions to provide heat to a medical product, such as frozen bags of blood or plasma, in order to thaw the frozen blood or plasma to a predetermined temperature for use in a selected medical procedure.
The heating apparatus includes a reservoir for holding a supply of heating fluid, such as water. A heating bladder is provided for engaging and heating the medical product. The bladder functions to receive heating fluid from the reservoir to effect indirect heat transfer from the heating fluid to the medical product. The bladder may include a bottom portion upon which a bottom surface of the medical product may rest and a top portion for covering a top surface of the medical product. The top portion and the bottom portion of the bladder are in fluid communication so that the heating fluid can transfer between the top portion and the bottom portion of the bladder during heating of the medical product. Such fluid communication allows any trapped air to flow from the bottom portion to the top portion so as to be out of contact with the medical product. The bladder may be in the form of an elongated bladder which may be folded in half so that one half of the bladder serves as the top portion and the other half of the bladder serves as the bottom portion so as to fold over and envelope the medical product.
A controller may be provided for controlling the heating of the medical product. A heater operates under the control of the controller for heating the heating fluid to a selected temperature. The heater may include a heating element disposed within the reservoir to effect the desired heating of the heating fluid.
A pump may be provided for operation under the control of the controller for pumping the heating fluid from the reservoir to the bladder. The pump may operate in a continuous mode or in a cyclical mode so as to control the flow of heating fluid to the bladder. A drain is provided in association with the bladder so that heating fluid from the bladder may drain back to the reservoir for reheating. The drain may be a passive gravity flow drain or an active drain that operates under the control of the controller. In operation, heating fluid that is heated in the reservoir may be pumped by the pump to the bladder to effect heat transfer to the medical product in engagement with the bladder. From the bladder, the heating fluid may be drained back to the reservoir where the heating fluid may be reheated by the heater to provide circulation of heating fluid through the bladder.
An agitator may be provided to agitate the medical product within the heating chamber to facilitate thawing. For this purpose, the agitator may be in the form of a motor-controlled rocker that rocks the heating chamber in order to promote thawing of the medical product within the heating chamber. In specific application, the rocker may operate under the control of the controller.
In order to detect any leakage of liquid within a heating chamber, a leak sensor may be provided. For example, sensor terminals may be provided within the heating chamber for detecting the presence of liquid within the chamber. The controller is responsive to the leak sensor for outputting an indication of the presence of liquid in the heating compartment. The controller may function to activate a visual or audible alarm reflecting a leak condition. Alternatively, the controller may function to completely stop the heating of the medical product in response to the detection of liquid in the heating compartment by the leak sensor.
A temperature probe may also be provided in the heating compartment for detecting the temperature of the medical product within the heating chamber. For this purpose, the temperature probe may be disposed within the heating compartment to engage the medical product to detect the temperature of such medical product. The controller operates in response to the temperature probe to control the heater to regulate the temperature of the medical product. In a programmed mode of operation, the controller may function to control the operation of the pump in response to the temperature probe to further regulate the temperature of the medical product. The controller may also operate in response to the temperature probe to stop the heating of the medical product when the temperature of the medical product detected by the temperature probe reaches a selected temperature.
An air filter may be provided in communication with the reservoir for filtering air relative to the reservoir. For example, when heating fluid is pumped from the reservoir to the bladder, ambient air is drawn into the reservoir through the filter to effect filtering of the intake of ambient air. Likewise, when heating fluid is drained from the bladder back into the reservoir, air in the reservoir may be exhausted through the filter to effect filtering of the exhaust air.
The heating apparatus may also be provided with a plurality of separate heating compartments and a plurality of bladders with at least one bladder disposed in each heating compartment to effect the simultaneous heating of multiple bags of frozen plasma. The individual heating compartments are separate from one another so that any leakage of liquid in one compartment is contained from any other compartment. Accordingly, if a medical product leaks into one compartment thereby contaminating such compartment, such contamination is isolated from the medical products in the separate heating compartments.